It is briefly mentioned in Dawidziak's "The Columbo Phile" (a wonderful book but sadly out of print and hard to find nowadays) as "an important step" for the show that while the strangling of Carol Fleming was gruesomely played out before the camera in "Prescription: Murder", later episodes (starting from "Ransom For a Dead Man") would either not show the murder at all or show it in a "sanitized" way. Obviously this was an intentional choice by the producers.

Of course, all those bloodless murders aren't exactly realistic, but it has never bothered me. "Columbo" is not about realism anyway...